1. Field of the Invention
The present invention relates to a thermoplastic elastomer composition with excellent heat fusion properties which can be bonded not only to a layer of an olefin type resin represented by a propylene type resin, but also to a layer of a nonolefin type resin such as an aromatic polycarbonate, acrylic resin, styrene type resin, vinyl chloride type resin, and a modified polyphenylene ether resin, to a composite molded product produced therefrom, and to a process for producing said composite molded product.
2. Description of the Prior Art
Conventionally, when (1) a crystalline olefin type resin layer and a polyester type thermoplastic elastomer, polyamide type thermoplastic elastomer or polyurethane type thermoplastic elastomer are to be combined together to produce a laminate, or (2) a nonolefin type resin layer such as an aromatic polycarbonate, acrylic type resin, and styrene type resin and an olefin type thermoplastic elastomer or styrene type thermoplastic elastomer are to be combined together to produce a laminate, since they are a combination of materials which can not be fusion-bonded together, such methods have been employed to produce composite products therefrom. In such methods, a combination of a recess and a projection are provided at the joint of the two different materials, a core material is partially covered with a surface material, or a hole is provided in a core material so that a surface material reaches the back side, to thereby bond them together mechanically, or an adhesive such as a primer is applied on the joint to make them into a composite molded product.
Accordingly, the resulting composite molded product has such problems as poor bonding strength between both layers, overly complicated structure or too many production steps.
As an attempt to solve such a problem, a method has been proposed in which an elastomer having polarity such as a polyester type thermoplastic elastomer, polyamide type thermoplastic elastomer, or polyurethane type thermoplastic elastomer is added to a nonpolar elastomer such as an olefin type thermoplastic elastomer, styrene/ethylene/butylene/styrene copolymer (hereinafter also simply abbreviated as "SEBS"), or styrene/ethylene/propylene/styrene copolymer (hereinafter also simply abbreviated as "SEPS"), as described in U.S. Pat. Nos. 5,002,625 and 5,149,589, or Japanese Patent Laid-open Nos. 2-147306 and 6-65467.
However, according to the method in which a polyester type thermoplastic elastomer, polyamide type thermoplastic elastomer or polyurethane type thermoplastic elastomer is added to an olefin type thermoplastic elastomer, SEBS or SEPS, the polyester type thermoplastic elastomer, polyamide type thermoplastic elastomer or polyurethane type thermoplastic elastomer is added in an increased amount that the resulting heat fusion property to the nonolefin type resin layer becomes satisfactory, the heat fusion property to the crystalline olefin type resin layer becomes almost nothing on the contrary.
Thus it has been difficult to carry out heat fusion to both the crystalline olefin type resin layer and the nonolefin type resin layer, and 1) heat fusion to the nonolefin type resin layer requires the olefin type thermoplastic elastomer, SEBS or SEPS to which the polyester type thermoplastic elastomer, polyamide type thermoplastic elastomer or polyurethane type thermoplastic elastomer is added, while 2) heat fusion to the crystalline olefin type resin layer requires a normal olefin type thermoplastic elastomer or styrene type thermoplastic elastomer; and this situation has led to such problems as a complicated molding process and a misuse of the molding material.
It has also been impossible to produce a composite molded product with a three layer structure comprising a nonolefin type resin layer/thermoplastic elastomer layer/crystalline olefin type resin layer.